Isobutanol is an organic compound, a form of lightweight alcohol, that is produced from natural and petrochemical sources and has many common solvent and some potential fuel uses. It is seen as a supplement or substitute for gasoline, as it is more energy intensive than ethanol and can be produced from waste agricultural and forestry products with a cellulose base, such as corn, sugarcane. and wood. Industrial uses for isobutanol include as a chemical intermediate in the manufacture of esters, in textiles manufacturing, and as a cleaning or polishing compound.
Since isobutanol is miscible with other common solvents such as alcohols, ketones, aldehydes and ethers, it lends itself to many chemical compounds and reactions in industry. The most common use for the chemical is in ester production, however, as a component of paint coatings such as lacquers. Its unique properties require that it only be added at concentrations of 5% to 10% to lacquer compounds. Other uses include in the manufacture of synthetic rubber, in the production of pharmaceuticals, and as a dehydrating agent, since it only partially mixes with water.
While isobutanol is not seen as a method of replacing petroleum-based fossil fuels due to the vast amount of organic source material that would be necessary to do so, it is seen as a key component of the alternative fuels industry. One of the advantages that isobutanol has over ethanol is that it can be blended with gasoline at any percentage rate. This is because it has an energy density and octane value that are closer to those of gasoline.
There are several methods for producing isobutanol, including those that use petrochemical precursors which are more commercially economical than biomass production as of 2011. An oil-based method is to run propylene, which is a colorless and gaseous alkene obtained from petroleum, through a hydroformylation reaction which produces 85% butanol and 15% isobutanol.
Reppe carbonylation, named after Walter Reppe, a renowned German chemist of the early 20th century, is a similar process that involves the addition of not just hydrogen such as occurs in hydroformylation, but also carbon monoxide and an iron catalyst. It was commonly used to produce isobutanol in Japan until 1984. The Reppe process differed from standard carbonylation in that the butanol alcohol products of the reaction were produced under milder reaction conditions, albeit with more chemical precursors.
As of 2010, around 3,000,000 tons of butanol were being produced per year for a variety of industrial uses, with a market value of $4,000,000,000 US Dollars (USD). The isobutanol segment of this market is estimated at $560,000,000 USD per year globally. Isobutanol production is growing rapidly in the US, however, as ethanol plants are converted over. Where ethanol only contains about 67% of the energy of an equivalent volume of gasoline, isobutanol contains 82%, and is not corrosive to pipelines like ethanol can be. A leading US producer of isobutanol plans an estimated production capacity of 350,000,000 gallons (1,324,894,120 liters) per year as of 2015.